1. Field of the Invention
The present invention relates to operations in a wellbore. More specifically, the invention relates to a system and method for steering a downhole device into a designated branch of a multilateral well circuit.
2. Description of the Related Art
Hydrocarbon producing wellbores extend subsurface and intersect subterranean formations where hydrocarbons are trapped. Well drilling techniques now include forming multilateral wells that include branches or laterals that extend from the motherbore. While most wellbores are lined with casing, sonic branched portions were left unlined to save cost, However, the openhole portions tend to produce an undesirable amount of water. While a workover on the well can be done to block water production, any workover involving entry into a branched portion can be lengthy, costly, and introduce risk due to uncertainties in entering the branched portion. Because branches are usually drilled using special drill steering devices, and are not easily accessible by most downhole tools. Entering a particular lateral is often done by trial and error using a bent-sub as a guide and rotating an associated tool string in order to orient the guide. A measurement while drilling (MWD) device on a tool is sometimes used to help orient the guide, and a retrievable bridge plug (also drillable) is sometimes installed in the motherbore in connection with these techniques to act as a temporary barrier. So if a lateral wellbore is tagged by any tool at the bottom of the string, the tool string can be pulled back up and reworked into the desired lateral wellbore. This is not always practical because typical completion equipment has a limited torque capability and often requires a ball operated pressure release device that precludes use of a MWD tool. Also, rotation completion equipment accidently across the window exit from the motherbore can damage the equipment. Existing sensing and guiding tool systems are typically conveyed on coiled tubing or on wireline. Another approach sometimes employed involves running and setting a retrievable whipstock in the exact location and orientation of a previous whipstock location, so that it can easily guide any work string into the lateral wellbore. However, this approach is not often attempted because setting a whipstock at an exact location and orientation along an existing wellbore remains a challenge; also retrieval of the whipstock may not be always assured.